1. Field of the Invention
This invention broadly concerns an artificial disc, insertion tool, and method of insertion for treating conditions of the human spine. More particularly, it is concerned with providing a system and method which advantageously permits insertion of the artificial disc from the posterior region of the patient and provides a unilateral approach with posterior stabilization through fixation through the pedicles of the vertebrae while still allowing the patient to enjoy a range of motion in the area of the artificial disc.
2. Description of the Prior Art
A number of conditions can result in damage or deterioration of one or more intervertebral discs of the human spine (hereinafter “discs”). A disc may become damaged by external injury or degenerative disc disease due to advanced age in combination with other factors, just to mention two examples. One condition which results in significant pain and potential nerve damage, and may require surgery, is a herniated disc.
One type of surgery which has benefitted patients with disc problems is fusion of the vertebrae adjacent the disc. In this surgery, the natural disc is replaced with a spacer and the vertebrae are fixed relative to one another. While such surgery provides a degree of relief to the patient, it necessarily limits flexibility of the spine, which presents a disadvantage for patients with an active lifestyle. Another disadvantage is the placement of greater loads on the adjacent vertebrae, resulting in what is commonly known as “adjacent segment disease.” Later efforts in the treatment of human disc problems is the use of artificial human discs. Conventionally, this treatment involves the removal of the natural human disc and the insertion of two plates through the abdomen, i.e. the anterior side of the patient. The reason that insertion through the anterior of the patient is thought to be the conventional method is that it avoids the necessity of passing the artificial disc past one or more of the spinal facets or articular processes, or the spinal cord. These body parts present significant obstacles to attempts to insert an artificial disc posteriorly. One problem with such conventional disc replacement systems and methods is that the anterior insertion of the disc does necessitate surgical involvement of the two major blood vessels, the vena cava and the aorta. Anterior insertion requires spreading the abdominal muscles and the aorta and vena cava in order to gain access to the vertebrae and the disc. Because rupture of either of the vena cava or aorta is life-threatening, such surgery requires the attendance of both a vascular surgeon as well as a spinal surgeon. Another problem is the difficulty presented in providing artificial discs in two pieces which provide satisfactory support and balance along a single load bearing point as close to the center load line of the spine as possible.
As a result, there has developed a need for an improved artificial disc which may be inserted unilaterally from the posterior side of the patient.
Moreover, there has developed a need for an improved artificial disc which provides support for the spinal column while providing the desired flexibility of movement.
Furthermore, there is a need for an improved artificial disc which minimizes the risk of injury to the patient during the surgical process.
In addition, there is a need for an improved method of insertion of an artificial disc which reduces the potential risk to the patient during surgery, minimizes or eliminates the necessity of spreading the abdominal muscles, and yet provides satisfactory insertion and stabilization of the disc.